346 Theories and techniques of oral implantology

cemented with hard cement (Fig. 9-36) and the implants and prosthesis x-rayed (Fig. 9-37) .

Case 4

Unilateral posterior free-end saddle restoration using a prefabricated prosthesis and vent-plants

If the operator so chooses, the final fixed partial denture may be fabricated prior to implant insertion. This approach has several advantages.

1. The entire time needed to complete the pros-thesis, insert the implants, and cement the bridge takes either two or three visits, depending upon whether elastic impression material or modeling compound tube impressions are used, respectively.

2. Because the finished prosthesis is fitted over the implants immediately after their insertion, fewer postoperative complications occur. Using the temporary splint technique generally involves removing and replacing the acrylic temporary splint several times. Also, the lapse of time between setting the implants and the final processing and cementing of the bridge invites complications. The ideal situation is to place the final prosthesis into position immediately after the implants are screwed into the bone.

With the prefabricated fixed partial denture technique, it is imperative that the patient wear the pre-fabricated denture for a day or two before the implants are inserted. Also, and even more important, the prosthesis should not be permanently cemented into position immediately after implant insertion. The bridge should be placed in the mouth temporarily, using cement only inside the crowns that cover the natural tooth abutments. The reason for the prosthesis' pretrial is to check for impingement of the pontics on the soft tissues. Severe pain can occur when the tissue-bearing surface of any pontic, usually its buccogingival line angle, presses into the underlying tissues. If there is a severe impingement, the constant pain suffered by the patient can often mislead the inexperienced dentist into believing that the pain results from the implants. A well-placed endosseous implant will cause no pain from the very onset. After a few trial days, the bridge is removed and all necessary adjustments are made prior to cementation with hard cement.

In this case, a three-unit fixed partial denture utilized the second bicuspid as the natural tooth abutment and two vent-plants.

On the first visit, the bicuspid was prepared for a full crown restoration. A full mouth wax inter-occlusal record of centric relation and an elastic impression, including the bicuspid and posterior

Fig. 9-38. A, A prefabricated three-unit porcelain-fused-tometal bridge. B, The undersurface of the bridge, showing lumens that accept the abutments. Note the retention pins inside the crowns, which facilitate the procedure.

edentulous area, were obtained. A full mouth upper alginate impression was also taken. The models were carefully articulated and a three-unit fixed partial denture fabricated (Fig. 9-38).

On the second visit, the three-unit fixed partial denture was positioned in the mouth, held only by the bicuspid preparation (Fig. 9-39). All necessary occlusal and gingival adjustments were then made and an x-ray taken to reevaluate the implant site (Fig. 9-40). At this point the operation may vary. If the cantilevered pontics were not made with openings for the implants, their undersurfaces should be marked with small indelible pencil marks. The bridge is replaced in the mouth and the pencil marks transferred to the fibromucosa over the alveolar crest. Generous holes are then drilled in the pontics to accept the implant posts. If the holes were pre-drilled, their rims should be marked and the marks transferred to the mucosa.

Using the transferred pencil marks as guides, the